Screen electrophotographic charge induction process

ABSTRACT

A charge induction electrophotographic imaging process wherein an insulating mesh is interposed between the photosensitive layer and the final record member.

United States Patent Seimiya et al.

SCREEN ELECTROPHOTOGRAPHIC CHARGE INDUCTION PROCESS Inventors: RyubunSeimiya; Yuzo Ohmuro; Sigeru Hanaoka; Masaru Nakamura, all of Tokyo,Japan Assignee: Konishiroku Photo Industry Co., Ltd.

Filed: Oct. 21, 1968 Appl. No.: 769,255

Foreign Application Priority Data [56] References Cited UNITED STATESPATENTS 3,512,966 5/1970 Shatluck et al. ..96/l 2,833,648 5/1958 Walkup....96/1 3,005,707 10/1961 Kallmann et al. ..96/1 3,011,473 12/1961Gundlach.... ..1l8/637 3,268,331 8/1966 Harper ..96/] 3,306,160 2/1967Dunhabel et a1 ..88/24 3,322,538 5/1967 Redington ...96/1.l 3,337,3398/1967 Snelling ..96/l 3,363,552 1/1968 Rarey ..101/l29 3,394,002 7/1968Bickmore ..96/l 3,449,568 6/1969 Vock ..250/49.5

Primary Examiner-George F. Lesmes Assistant Examiner-John C. Cooper, 111

Attorney-Harry C. Bierman, Jordan B. Bierman and Bierman and Bierman [57] ABSTRACT A charge induction electrophotographic imaging processwherein an insulating mesh is interposed between the photosensitivelayer and the final record member.

11 Claims, 38 Drawing Figures .lllll l i Pa e! April 4, 1972 3,653,890

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mum/1v SEIMIYA, YUZO ofimum SIGERU HANAOKA \f- NASARU NAKAMURAA'r-reR-NEYS SCREEN ELECTROPHOTOGRAPHIC CHARGE INDUCTION PPOCESS Theinvention relates to improvements in or relating to anelectrophotographic process, and more particularly, to novel means forpreparation of an electrostatic latent image on a record member, andalso to a radiation sensitive member which is subjected to imagewiseexposure to an original to be reproduced and conveys image informationto the final record member. The invention also relates to intermediateand final record members for use with such process.

The known electrophotographic process such as Xerography or Electrofaxemploys a layer of photoconductive material which is uniformly chargedin darkness by corona discharge and then exposed imagewise to form anelectrostatic latent image thereon. The latent image is developed by atoner, and the Electrofax process fixes the developed image on thephotoconductive layer, while in the Xerography, the developed image istransferred onto an image receiving member to be fixed thereon. Usualphotoconductive layer used in the Xerography comprises a deposited filmof amorphous selenium and the residue of toner which remains unremovedon the selenium film during the transfer must be cleaned to ensuresatisfactory operation of the film when used repeatedly. However, thefilm surface is susceptible to damage by the cleaning operation owing toabrasion by toner powder and cleaner brush, thereby causing adegradation in the image quality. There have been several proposalswhich avoid such disadvantage by transferring an electrostatic latentimage on the selenium film directly onto an insulating record memberbefore the image is developed, as disclosed in US. Pat. No. 2,982,647.Alternatively, an electrostatic latent image is formed on an insulatingrecord member while holding it at a very small distance of air gap froma photoconductive member during imagewise exposure with a voltage beingapplied simultaneously across the both members, as disclosed in US. Pat.Nos. 2,825,214, 2,833,648 and 2,937,943 issued to LB. Walcup. However,these approaches involve technical difficulties in maintaining aconstant and uniform air gap between the members and are dissatisfactoryin their commercial utility.

Therefore, it is an object of the invention to provide an improvedelectrophotographic process and apparatus for preparation of anelectrostatic latent image on a final record member which is technicallyreadily feasible and lends itself to continuous recording with goodimage quality.

It is another object of the invention to provide a novel radiationsensitive member which serves to convey image information from anoriginal to a final record member in the form of an electrostatic latentimage.

Fundamentally, according to the invention, the electrophotographicprocess of forming an electrostatic latent image on an insulating recordmember held in contact with another member while a voltage is beingapplied thereacross is characterized in that one or the other of themembers has a thin insulating layer of a mesh pattern on its surface,which abuts against the other or said one of the members.

In one aspect, the process according to the invention em ploys aradiation sensitive member comprising a radiation sensitive layer onwhich is formed an insulating layer of a mesh pattern. The termradiation sensitive layer is intended herein to mean a normallyelectrically insulating layer which obtains an increased electricalconductivity upon exposure to radiation of any suitable wavelength,including corpuscular ray and X-ray. Usually such layer may comprise asuitable known photoconductive material when light is chosen as acarrier of image information. Where X-ray is used as the image carrier,a deposited film of amorphous selenium may be used as such layer. Arecord member of an insulating material is held against the mesh layerof the radiation sensitive member and a voltage is applied across theboth members for a short period during which the composite is exposed toradiation image of an original to be reproduced. This forms anelectrostatic latent image of the original on the insulating recordmember, which image is developed and fixed subsequent to separation ofthe record member from the radiation sensitive member.

Alternatively, the radiation sensitive member may be initially formedwith a latent image thereon by a separate process which may comprise anyconventional means. The member is then placed in close contact with afinal record member, and then a voltage is applied between the bothmembers. Transfer of the latent image occurs from the radiationsensitive member to the record member by migration of electric chargesthrough the spaces defined by the patterned dots of the mesh layer.

Preferably, the radiation sensitive member comprises a substrate havingsufficient mechanical strength to withstand the pressure with which aninsulating record member is pressed thereagainst. The substrate may beeither insulative or conductive and when it is insulative, it shouldhave a conductive surface commensurate in area with the radiationsensitive layer. The radiation sensitive layer may form an ohmic contactwith the substrate, or a barrier which prevents injection of free chargecarrier may be formed between the layer and the substrate. In the formercase, the time constant, T, when charge is being supplied to the surfaceof the radiation sensitive layer by dark current is given by I 1- K, p,r 1 where K, denotes dielectric constant of the layer material, spermittivity in vacuum and p resistivity of the layer material when notexposed to radiation, which may be referred to hereinafter as darkresistivity. When both the radiation sensitive member and the insulatingrecord member are exposed to imagewise radiation while in contact, thetime period of voltage application required for the formation of thelatent image must be at least equal to the exposure time, t thus 1' e t(2) The time t depends on the sensitivity of the radiation sensitivelayer and the intensity of radiation used. For example, when a depositedfilm of amorphous selenium is used with a light source which comprises atungsten incandescent lamp providing illumination of luxes on thesurface of the selenium film, t will be 0.2 second. Thus, in thisinstance, p e 3 X 10 (2 cm. Amorphous selenium usually has a p-value ofthe order of 10 S cm. and hence is suitable for the purpose of theinvention.

When a barrier is formed between the radiation sensitive layer and theconductive substrate which prevents injection of free charge carrier,the density of charge, 0, induced on the layer surface by application ofthe voltage will be given by s e (3) where n denotes the concentrationof free charge carriers in the layer, 1,, the layer thickness and e thecharge of a charge carrier. Assuming uniform distribution of donors oracceptors in the layer, the reverse electromotive force or polarizationvoltage caused by induced charges will be as follows:

where 1,, and K denote the thickness and dielectric constant of a recordmember, respectively, Z the length of air gap provided by the patterndots between the both members and D is given by the following equation:D=l,/K,+l /K 5 The maximum permissible value of V, depends upon variousfactors, but for the purpose of illustration, it will be assumed here tobe 100 v. and when other parameters assume the following values:

l /K,,= 3 microns l, /K,= 10 microns l, 63 microns Z 10 microns then thepermissible concentration of charge carrier will have to be n e 3 X 10cm. Using this figure, the dark resistivity, p, of a radiation sensitivelayer having mobility p. of 1 cm. /v.sec. is calculated to be p 2 X 100. cm.,

which is nearly 10 times less than the necessary value in an ohmiccontact system. In practice, however, there will be no contact whichconstitutes a potential barrier capable of completely suppressinginjection of charge carrier. Thus the possibility of a small leakagecurrent, I,,,, must be catered for which builds up a potential on thesurface of the radiation sensitive layer. The charge accumulation isproportional to the time period of voltage application, and placing theresulting voltage equal to V, given by the equation (4), we have,

d s o/ s) P O) Assuming V, 100 v., K,/l,= 10 cm. and t 0.2 second,

I 5 5 X lo 8 A.

This is the value below which the leakage current of the radiationsensitive layer must be held.

When the radiation sensitive layer is formed with a latent image beforeit is held in pressed relationship with a record member, the time lengthfrom the formation of a latent image on the radiation sensitive layeruntil completion of transfer will be greater, that is, the factor t willbe by about ten to hundred times greater than before, so that it isrequired that the dark resistivity be greater and the leakage current besmaller at corresponding proportions.

The process mentioned above depends for its operation upon the migrationof electric change to the surface of a record member in those parts ofthe space defined by the dots of the mesh layer which correspond toirradiated parts of the radiation sensitive member. This requires theapplication of a sufficiently high voltage, which in turn necessitatesto ensure good insulation of the mesh layer. Experiments have shown thatthe mesh layer should have a resistivity not less than 10 cm. and asurface resistance not less than 10 (I per square. The thickness of themesh layer determines the length of the air gap between the radiationsensitive layer and the record member, and in order to ensure good imagequality of the latent image, the thickness should be within a range from0.5 to 100 microns, preferably from to 20 microns. Additionalrequirements imposed upon the material of the mesh layer are that it ishighly adherent to the surface of the radiation sensitive layer, that itdoes not exhibit any aggressive behavior to the surface to causedegradation of its characteristics and that it has sufficient mechanicalstrength and durability to withstand repeated use.

Such mesh layer may be formed in various ways. In one example, aphotopolymerizable material e.g. photoresist available from EastmanKodak Company under the trademark of KPR or KMER is applied on aradiation sensitive layer to a thickness given above. After drying, itis exposed to ultraviolet ray through a mask of suitable pattern andunilluminated parts are removed by a developer principally comprisingtrichlene. After drying, the remaining photoresist is fixed. Thisprovides a meshwork of very high resolution. Alternatively, conventionalelectrophotographic process proposed by Carlson may be used to form anelectrostatic latent image of desired pattern on a radiation sensitivelayer, and the latent image may be developed by an insulating toner andfixed. In this instance, the thickness can be controlled by theintensity of charge provided by corona discharge or by the intensity ofexposure. Typical materials for the mesh layer includes polyethylene,polystyrene, polyester, polyamide, Teflon (trademark), vinyl chloride,vinyl acetate, phenol resin and co-polymers of these materials.

Where the mesh layer has a poor adherence to the underlying radiationsensitive layer or when it is desired to prevent any reaction with thelatter, a substratum may be provided on the radiation sensitive layer.When the substratum has a thickness not less than 0.5 micron, and up tothick of the radiation sensitive layer, it is found that the provisionof such substratum has no substantial influence upon the image quality.As known, such substratum may also serve to reduce mechanical abrasionof the radiation sensitive layer.

As mentioned previously, the dark resistivity required for a radiationsensitive layer can be reduced by several orders by providing a thininsulating layer, between the conductive substrate and the radiationsensitive layer, which prevents injection of charge carrier. The leakagecurrent through such thin layer must be held below the value estimatedby the equation (6) and its thickness should be chosen so as not todegrade the contrast of the image, which would be satisfied when thethickness is below about 10% of that of the radiation sensitive layer.In addition, the radiation sensitive layer may comprise more than onelayers to increase the quantum efficiency during the formation of thelatent image.

In another aspect, the process according to the invention employs afinal record member which has on its insulating recording layer aninsulating layer of a mesh pattern. The mesh layer may be similarlyconstructed as that of the radiation sensitive member described above.In addition, the insulating recording layer and the mesh layer may beformed integrally. The thickness and resistivities of the mesh layer aresimilar to those indicated previously. In this instance, the formationof an electrostatic latent image on the record member is effected byusing a radiation sensitive member having a radiation sensitive layersupported on a substrate, the layer being pressed against the mesh layerof the record member. The major difference from the first mentionedprocess is that the radiation sensitive member used in this instancedoes not have a mesh layer, which is transposed onto the final recordmember.

Such mesh layer of the record member may be formed in various ways, andthe techniques described above in connection with the preparation of theradiation sensitive member may be used. Alternatively, a copperplate ofdesired pattern and depth is prepared and is filled with a copperplateink for printing on a recording layer. Such copperplate ink comprises anon-colored transparent solution which becomes electrically insulatingupon drying and solidification, such for example as a transparent resinsolution of relatively low viscosity. Excessive ink attaching to thesurface of the copperplate is doctored off. When the recording layer andthe mesh layer are formed as integral, a thermoplastic resin such aspolystyrene is coated on a support or formed into a single-layered filmas by extrusion or casting technique and pressed against a heated matrixwhich is previously formed on a metal roll in a desired pattern and witha desired depth. Upon removal of the resin film from the matrix, theresin film will have a mesh-shaped unevenness formed on its surface. Inthis operation, suitable choice of the roll temperature, pressing timeor the relative speed between the roll and the film is important. Tofacilitate detachment of the film, it is preferred to shape the matrixso as to provide tapering dots in the form of truncated cone or pyramid.Application of higher fatty acids such as stearic acid, as a remover, onthe matrix surface may be effectively used.

In a further aspect, the process according to the invention employs anintermediate record member which comprises an insulating recording layeron which is formed another insulating layer of a mesh pattern. Theconstruction, material and sizes of the intermediate record member maybe same as the record member described just above in connection with thesecond process. When preparing an electrostatic latent image on a finalrecord member according to this process, the intermediate record memberis held pressed against a radiation sensitive member in the first step,the radiation sensitive member used in this process comprising aradiation sensitive layer on which no mesh layer is formed. In thesecond step, the intermediate record member is held in close contactwith a final record member. In each of the first and second steps, ahigh voltage is applied between the respective two members held incontact to effect transfer of a latent image from one to another.Imagewise exposure is effected in the first step simultaneously with theapplication of the voltage.

In all of the processes described above, it is essential for bestresults to ensure a close and uniform contact between mating memberswith proper spacing provided by patterned dots. Suitable means thereforwill be described later with reference to various embodiments.

For better understanding of the invention, it will be described in moredetail with reference to the drawings, in which FIG. I is a schematicsection to an enlarged scale of a novel radiation sensitive memberaccording to the invention,

FIG. 2 is a similar view of a modification of the member shown in FIG.1,

FIG. 3 shows various patterns of the mesh layer,

FIG. 4 is a schematic view illustrating the process of the inventionusing a radiation sensitive member with a mesh layer,

FIG. 5 is a similar view where the radiation sensitive member is not,but the record member is transparent to radiation,

FIGS. 6a to 60 show the process in which a latent image is formed on theradiation sensitive member prior to its contact with the record member,

FIGS. 7a and 7b show the process in which a positive is obtained,

FIG. 8 is a schematic view of a copying machine in which the processshown in FIG. 4 is employed,

FIGS. 9a to 9d are sections of various forms of a record member used inthe second manner of the process according to the invention,

FIG. 10 is a schematic view illustrating the process using the recordmember shown in FIG. 9,

FIG. 11 is a view schematically illustrating a preferred manner ofensuring good contact between a radiation sensitive member and a recordmember,

FIGS. 12a and 12b show the process using the record member of FIG. 9 inwhich a positive is obtained,

FIG. 13a to 13 show another manner of the process using the recordmember of F IG. 9 in which a positive is obtained,

FIG. 14a to 14d are schematic sections of an intermediate record memberused in accordance with the third aspect of the process according to theinvention,

FIGS. 15a and 15b show a manner of carrying out the process forformation of an electrostatic latent image on a final record memberusing the intermediate record member shown in FIG. M, I

FIGS. 16a to 16d show another manner of the process with theintermediate record member of FIG. 14, and

FIGS. 17 to 21 show various forms of a copying machine incorporating theintermediate record member of FIG. 14.

Referring first to FIGS. 1 to 8 inclusively, which show the radiationsensitive member proposed by the invention and processes and apparatuswhich use the member, this member is generally shown in FIG. 1 byreference numeral 1 and includes a conductive substrate 2, and aradiation sensitive layer 3 as defined above which is evaporated on thesubstrate or coated thereon in the form of a dispersion in resinousbinder. On the layer 3 is secured an insulating layer 4 which has a meshpattern as shown in FIG. 3. In FIG. 3, black portions may represent aninsulating material and white portions spaces therebetween or viceversa, and the pattern may comprise any regular or irregular array ofdots, lines, solid triangles, diamonds or the like which can represent apicture element. Usual halftone or crossline screen pattern widely usedin the art of printing may be suitable for the pattern of the insulatinglayer 4. Preparation and useful thickness of such mesh layer has beenmentioned previously. The radiation sensitive member shown in FIG. 2 isgenerally similar to that of FIG. 1 except that the substrate 2 is of aninsulating material and has a conductive thin film 2' deposited thereonto provide an electrode.

Referring to FIG. 4, the process of forming an electrostatic latentimage on a record member 5 with using the above radiation sensitivemember 1 will be described. The record member 5 comprises an insulatingrecording layer 6 on a conductive base 7, but the record member may be acommercially available electrostatic recording sheet. As shown, both themembers 1 and 5 are positioned on a counterelectrode 8, with the meshlayer 4 abutting against the insulating recording layer 6. Suitablepressure in the order of from 0.1 to l kg./cm. is applied between thesubstrate 2 and the electrode 8 to cause a close and uniform contactbetween the both members. The electrodes 2', 8 are connected to a DCsource 9 through a switch 10 and are also interconnected by anotherswitch 11. In the example shown, it is assumed that the substrate 2 andconductive film 2' are both transparent to radiation 12 which is usedfor the imagewise exposure. Such substrate and electrode can be formedwith Nesa glass, for example.

Upon closure of the switch 10, a high tension is applied across theelectrodes 2, 8, and as the assembly is exposed to radiation 12, freecharge carriers, electrons or positive holes, created by irradiationmove to the surface of the layer 3 under the influence of the electricfield, so that there is produced a very strong field in the spacebetween the layers 3 and 6. For this reason, there occurs migration ofelectric charge to the layer 6 through the air space left between theland or mesh material 4, so that there will be provided electric chargeon the surface portions of the recording layer 6 which face the airspace in the mesh layer 4 in the region exposed to radiation 12. Thenswitch 10 is opened followed by closure of switch 11, whichshort-circuits the members. Subsequently the record member 5 isseparated from the member 1 and the latent image thereon is developedand fixed. The density of such surface charge on the recording layer 6has a tendency to increase with an increasing amount of exposure, butsaturates at a value which depends on the film thickness and dielectricconstant of the layers, the characteristics of the radiation sensitivelayer, the magnitude and polarity of the voltage applied and otherfactors. However, excessive exposure is objectionable because of spreador blur of a resulting image. The polarity of the voltage may bearbitrarily determined in most cases, but a particular polarity may besometimes preferred depending upon the kind of the radiation sensitivematerial used. The optimum value of the voltage applied depends upon thethickness and dielectric constant of various layers, and an example willbe given below.

Amorphous selenium was deposited on a Nesa glass to a film thickness of50 microns and a mesh layer 10 microns thick of KPR was provided on thefilm. A record member comprised a film of Mylar 12.5 microns thickhaving a deposited aluminium film. These members were pressed togetherand to the surface of Nesa glass was applied a voltage of l,120 volts.After irradiation of a light image for one second with maximumillumination of 20 luxes on the image surface, the Nesa glass surfaceand the deposited aluminium film were short-circuited. Then the recordmember was separated from the Nesa glass and the latent image on theMylar film surface was developed with a magnetic brush. The developedimage had satisfactory image quality.

It is to be noted that synchronization of the exposure with theapplication of the voltage, though preferred, is not essential in themanner of operation shown in FIG. 4. It is sufficient to provideexposure during application of the voltage. However, the exposure timeconcurrent with the voltage application is the effective exposureperiod, which must be long enough to form an electrostatic latent imageon the record member.

A suitable insulating record member 5 may be formed by providing aninsulating recording layer on a flexible conductive support, such as aso-called electrostatic recording sheet which comprises a thininsulating recording layer applied on a paper which has been treated tobe conductive. Also it may comprise a flexible insulating materialprovided with a thin conductive coating on one surface thereof, e.g.polyester film with deposited metal such as aluminium; a transparentinsulating material with a transparent conductive layer which maycomprise SnO TiO Cul or the like; or a film of insulating resin alone,whether transparent or opaque, which has resistivity and surfaceresistance sufficiently high to retain an electrostatic charge, forexample, polyethylene, polystyrene, polyester, polyamide, Teflon(trademark), vinyl chloride, vinyl acetate, phenol resin or the like.Thus the record member 5 can be constituted by a single layer of aninsulating material, which preferably is flexible to ensure good contactwith the radiation sensitive member.

It will be appreciated that both the radiation sensitive member 1(except mesh layer 4) and the record member 5 are not completely plane,but include surface roughness and undulations so that such unevennesscauses irregularities in the degree of close contact between thesemember particularly when the electrode 8 comprises a rigid material suchas metal, thereby resulting in the degradation of image quality. Suchdisadvantage can be eliminated by using the electrode 8 which is madefrom a soft, elastic material. Such soft, elastic electrode 8 shouldhave sufficient thickness and deformability to compensate for thesurface roughness and undulations. A conductive rubber sheet 1 cm. thickproved satisfactory for this purpose. When such soft, elastic electrode8 is used, it is desirable to provide a support on the back of theelectrode 8 for the convenience of applying pressure and such supportcan be formed from metals or plastics material of relatively highstrength such as bakelite.

FIG. 5 shows another manner of the above process which is employed witha radiation sensitive member having an opaque conductive substrate. Inthis instance, a record member 5 consists of a transparent insulatingfilm 6, e.g. a film of polyester resin, and a transparent conductivefilm 7 such as copper iodide. The electrode 8 is constituted by atransparent conductive material and is supported on a transparentsubstrate 8 which may be formed with Nesa glass. Radiation 12 is appliedthrough the transparent layers 6 to 8 and 8. The operation of theprocess is the same as in FIG. 4.

The radiation sensitive member 1 may be previously formed with anelectrostatic latent image before being placed in contact with therecord member 5. An example of such manner of operation is illustratedin FIGS. 6a to 60, where like parts are designated by same referencenumerals, but the electrode 8 is replaced by a roller and the switch 10is a double pole-double throw switch rather than a single pole switch asin FIGS. 4 and 5. Also for the sake of brevity, the insulating meshlayer 4 is shown in continuous lines, but it should be noted that it isformed in a pattern as shown in FIG. 3. Initially the switch 10 isthrown to the position shown in FIG. 6a, and the roller 8 is moved fromleft to right while rolling, thereby providing a high negative potentialto the conductive substrate 2 and providing a positive charge to thelower surface of the radiation sensitive layer 3 through the air spacein the mesh layer 4. Then the member I is exposed to imagewise radiation12 (FIG. 6b), thereby forming an electrostatic latent image thereon. Nowthe member I is superimposed on a record member 5. The switch 10 isthrown to the other position as shown in FIG. 6c, and the supply voltageis applied across the conductive substrate 2 and the roller electrode 8with the substrate 2 positive (FIG. 6c). As the roller 8 is moved fromleft to right while pressing the record member 5 against the radiationsensitive member I, the latent image is transferred from the latter tothe recording layer 6. Then the switch 11 is closed to remove chargefrom the member 5 and the two members 1, 5 are separated from eachother.

Another manner of forming a latent image on the radiation sensitivemember 1 prior to its contact with a record member is shown in FIGS. 7aand 7b. Here, the member 1 has a transparent substrate 2 and atransparent conductive layer 2, as shown in FIG. 2, and initially anegative potential is applied to the electrode layer 2 with respect tothe roller electrode 8, which is moved from left to right, as shown.However, in this instance, there is provided a light shield 13 having aslit 14 above the member 1. The light shield is arranged to be slidablein a plane parallel to the member 1, and as the roller 8 moves to theright, the light shield 13 also moves in the same direction at the samespeed. During such movement of the roller 8 and light shield 13, themember 1 is exposed imagewise to radiation 12 through the moving slit14. Thus negative charges will be produced on the surface of theradiation sensitive layer 3 not covered by the patterned mesh layer 4.Then the radiation sensitive member 1 having a latent image thus formedthereon is superimposed on a record member 5 (FIG. 7b), and whileapplying the voltage, the roller 8 is again moved from left to right tourge the record member 5 against the radiation sensitive member 1,whereupon the latent image is transferred onto the insulating recordinglayer 6.

While in the above embodiments, charges are produced on the recordinglayer 6 at positions subjected to radiation 12 so that the imagedeveloped will be a negative, it is possible in FIG. 7b to reverse thepoarity of the voltage applied to obtain a positive.

Several examples of the above process and radiation sensitive memberwill be given below, which however should not be construed as limitationto the invention.

EXAMPLE 1 v A substrate was prepared by using a hard glass 2 mm. thickto deposit thereon a thin film of tin oxide, which is usually called aNesa film. On the Nesa film was applied an evaporated film of amorphousselenium to a thickness of 50 microns. An 8 micron thick layer of KPRwas formed as a mesh layer on the selenium film. The meshwork comprisedthin fiat discs of KPR having a diameter of about 50 microns which werearranged in a regular form with spacing of about 75 microns, providing200 meshes. This constituted a radiation sensitive member. Such memberwas used together with a commercially available electrostatic recordingsheet in the process generally similar to that illustrated in FIG. 4.The urging electrode used was a conductive rubber sheet having athickness of 1 cm. and hardness of 30 (JIS), and pressure of about Ikg./cm. was applied to press the radiation sensitive member and therecord member together. Applying +750 volts to the conductive Nesa filmand using an exposure of 20 lux-sec. from a photographic enlarger, alatent image of good image quality was obtained.

EXAMPLE 2 On the same Nesa glass substrate as used in Example I wasapplied a thin film, about 2 microns thick, of thermosetting epoxy resinand on the resin film was coated a mixture, in equal volume proportions,of fine powder of cadmium sulfide activated by copper and thermosettingsilicone resin as binder. A mesh layer 10 microns thick was prepared onthe coating in the similar manner as in Example 1, using Dycril,photopolymerizable resin available from Du Pont Company. Using aradiation sensitive member thus formed and a commercially availableelectrostatic recording sheet in the similar process as in Example 1,with the voltage of -l ,200 volts and exposure of 5 lux-sec., a latentimage of good image quality was obtained.

EXAMPLE 3 On one surface of a 1 mm. thick alumium plate was formed analumina film having a thickness of 500 A. by plasma oxidation technique.On the alumina film was provided the coating of cadmium sulfide-siliconeresin dispersion, used in Example 1 2, to a thickness of 50 microns.After setting of the coating, a KPR mesh layer, 8 microns thick and 200meshes, was applied thereon, thus completing a radiation sensitivemember. This member was used in the process illustrated in FIGS. 6a to6c. The voltage used in the step of FIG. 6a was --1 ,500 volts, theexposure in FIG. 6b was 5 lux'sec., and the voltage applied in the stepof FIG. 60 was +900 volts. The roller speed was 20 cm./sec. and theurging force of 10 kg. weight was used. The latent image obtained showedgood image quality.

EXAMPLE 4 On the same Nesa glass substrate as used in Example 2 wasapplied an epoxy resin layer about 2 microns thick on which wasevaporated crystalline selenium to a thickness of 1 micron followed byfurther evaporation of amorphous selenium to a thickness of 50 microns.On the surface of the latter was applied a mesh layer of KPR, 8 micronsthick and 200 meshes as in Example l. The radiation sensitive memberthus formed was used in the similar process as in Example 1 and provideda latent image of good image quality, but the exposure required waslux-sec., showing that the present radiation sensitive member had fourtimes as high a sensitivity as that of Example 1.

EXAMPLE 5 On an aluminium plate 1 mm. thick was evaporated a layer ofamorphous selenium to a thickness of 100 microns and on the seleniumlayer was applied a mesh layer of KPR microns thick. This radiationsensitive member was used in the process illustrated in FIG. 4, butusing the conductive rubber electrode as in Example 1. A pressure of lkg./cm. was ap plied to the electrode. The exposure to an X-ray image ofmaximum dosage rate 450 mr./sec. for one second during application of+1,200 volts produced an electrostatic latent image of good quality. Therecord member used in Examples 3 to 5 were commercially availableelectrostatic recording sheets, and the latent image was developed witha magnetic brush.

FIG. 8 shows a copying machine which is constructed to carry out theprocess illustrated above. The machine includes a stationary lightsource such as a lamp 20, which serves projection of the image of atransparent original 21 through an optical system 22 and a slit 23 in afixed light shield 24 onto a radiation sensitive member 25. The member25 includes a transparent conductive substrate which is earthed as shownand its radiation sensitive or photoconductive layer is disposed to facea continuous web of record member 26 as the latter is moved past aconductive rubber electrode 27, the record member 26 being supplied froma roll 28 through a pair of guide rollers 29. The member 25 is arrangedslidable horizontally as indicated by a both-ended arrow, and thearrangement is such that as the original 21 is moved to the left, asviewed in this Figure, at a constant speed, the members 25, 26 are movedto the right at the same speed as the speed of the focussed image, sothat the image of successive parts of the original 21 is focussed on thecorresponding contiguous parts of the record member 26. The rollerelectrode 27 is made from conductive rubber and is rotatably carried ona vertically movable support 30. A DC source 31 has its one terminalconnected with a finger 32 which contacts the roller surface forapplication of a suitable voltage, and the other terminal of the sourceis earthed. Suitable means is provided, though not shown, to maintain atension in the record member 26 and to drive it, when necessary, pastthe roller 27, guide rollers 33, 34, a developer unit 35 and a fixingunit 36 to a take-up spool 37.

In operation, before the original is set in motion to move one frame ofthe original below the lamp 20, the support 30 is raised upward to causethe roller 27 to urge the record member 26 against the photoconductivelayer or move precisely the mesh layer of the radiation sensitive member25, and as the original starts to move, both the members 25 and 26 arefed to the right at the same speed as the original. The lamp and thesource are turned on, and then an electrostatic latent image is formedon the record member 26. Upon termination of the motion of the originalby a distance of one frame, the forward drive is interrupted for aperiod, and the support 30 is lowered to release the record member 26from contact with the member 25, which is then allowed to return to itsinitial position. Then the machine is ready for another copying cycle.The latent image on the record member 26 is developed and fixed beforethe latter is taken up on the spool 37.

As mentioned previously, the process according to the invention isoperable with a record member which includes on its insulating recordinglayer a mesh layer of the kind specified above. Such record member isshown in FIGS. 9a to 9d, and FIGS. 10 to 13 inclusively show the mannersof the process using such record member.

Referring to FIG. 9a, such record member is generally shown at 50 andconsists of an insulating layer 51 adapted for use as a record carrierand another insulating layer 52 of a mesh pattern as indicated in FIG.3. The material for such mesh layer 52 as well as its thickness andelectrical properties should be similar to those described withreference to the mesh layer of the radiation sensitive member shown inFIGS. 1 and 2. However, the layers 51 and 52 may be formed with samematerial and hence integrally as shown in FIG. 9b, where the recordmember 50 includes a conductive layer 53. The record member shown inFIG. 9c has a substrate 53 which may be electrically conductive orinsulating. Numeral 54 denotes a substratum which prevents penetrationof a solvent that is used when coating the insulating recording layer 51on the substrate. Such substratum may be formed by using a water solubleresin such as polyvinyl alcohol or any other suitable material that isinsoluble to the solvent used for the coating of the recording layer.Such substratum can be omitted in certain circumstances depending uponthe nature of the substrate material and the coating technique used.FIG. 9d shows a modification of FIG. 9c where the layers 51 and 52 areintegral. Suitable material for the recording layer 51 includespolyethylene, polystyrene, polyester, vinyl acetate, phenol resins ortheir copolymers, and the choice will be made from consideration ofcharge retention, film plasticity, flexibility, surface characteristics,compatibility with coating, economic factors or the like. The recordinglayers in FIGS. and 9d need not be transparent, but they may comprise adispersion of fine white powder such as titanium or zinc oxide in any ofabove resins. However, the record member 50 having the mesh layer musthave sufficient flexibility to ensure the forma tion of a uniform latentimage. Flexibility found in commercially available electrostaticrecording papers is satisfactory.

FIG. 10 shows a manner of the process of forming a latent image on arecord member 50 of the type shown in FIG. 9c, and numerals 8 to 12denote parts designated by corresponding numerals in FIGS. 4 and 5. Forthe convenience of description, it is assumed here that light is used asradiation 12. Then a photoconductive member 55 is used which comprisesan integral lamination of a transparent substrate 56, a transparentconductive layer 57 and a photoconductive layer 58, which may be ofsimilar material as used in Carlson process. The member 55 is placed onthe member 50 with the photoconductive layer 58 abutting against themesh layer 52, and the composite is positioned on an electrode 8.Suitable means (not shown) is used to press the both members togetherwith a pressure of from 0.1 to 1 kg./cm. for example. The conductivelayer 57 is connected through switch 10 to the positive terminal of a DCsource 9, of which negative terminal is connected to the electrode 8. Inaddition, the electrode 8 and the layer 57 are interconnected through aswitch 11. When the switch 10 is closed and radiation 12 is releasedimagewise, there will be produced positive charges on the surface of thephotoconductive layer 58, opposite to the insulating recording layer 51,where subjected to the exposure. Such surface charges produce anelectric field of sufficient strength to cause migration of charge tothe layer 51, thereby forming an electrostatic latent image on thesurface of the recording layer 51. Upon termination of the exposure, theswitch 10 is opened and the switch 11 is closed to short-circuit thelayer 57 and the electrode 8. Then the both members 50 and 55 areseparated and the latent image on the recording layer 51 is developed.

The electrode 8 may be constituted by a soft, elastic material such asconductive rubber and a separate pressure plate may be urged against theback of the electrode in order to apply pressure, thereby ensuring closeand uniform contact between the both members. The record member shown inFIGS. 9a and 9b may be equally employed in above process.

FIG. 11 shows a convenient method of assuring a close contact betweenthe members. The record member 50 having a mesh layer and thephotoconductive or radiation sensitive member 55 are disposedhorizontally in superimposed relationship. The member 50 comprisestransparent materials entirely and its conductive layer 53 is connectedwith one terminal of a DC source 9 through a switch 10. The member 55has a conductive substrate 56 which is connected with the other terminalof the source. In this particular arrangement, the member 55 has aradiation sensitive layer 58 of such size and configuration that leavesa free marginal area of the conductive substrate 56 all around theradiation sensitive layer 58. The both members are covered by anair-tight and transparent film 60, such as Mylar film, which is sealedat its opposite ends and side edges with the conductive substrate 56 bysuitable means indicated at 61. In an end part of the conductivesubstrate 56 is formed an opening 62, which is connected to a suctionmeans such as vacuum pump. The space enclosed by the film 60 is partlyevacuated, for example, to 0.8 atm.,

- and such sub-atmospheric pressure serves to achieve a close anduniform contact between the both members 50, 55. Then the switch isclosed and radiation 12 is released. It is to be noted that while highvacuum is favourable to make the contact closer, it renders the chargemigration through the air space between the both members difficult tooccur, thereby requiring a higher voltage for the source 9.

In FIGS. 10 and 11, there will be an electric charge in the irradiatedparts of the record member and therefore such charge provides a negativewhen developed. However, the process illustrated in FIGS. 12a and 12bprovides a positive. In these Figures, the radiationsensitive member 55totally comprises transparent materials and the electrode 8 is in theform of a roller. In addition, the switch 10 is a double-poledoublethrow switch. Initially, a negative potential is applied to theconductive layer 57 of the radiation sensitive member 55 from the DCsource 9 and at the same time the assembly 50, 55 is exposed to uniformradiation from the side of the member 55. During such exposure, theroller 8 is moved from left to right while rolling to press togethersuccessive parts of the members 50, 55 (FIG. 12a). This step charges therecord member 50 uniformly. Then the roller 8 is returned to the left,and a light shield 63 having a slit 64 is arranged above the assembly inparallel thereto (FIG. 12b). The switch 10 is thrown to the otherposition and thus a positive potential is applied to the conductivelayer 57. Then the radiation 12 which is defined imagewise is releasedand the roller 8 is moved to the right as before. Simultaneously, thelight shield 63 is moved to the right at the same speed as the roller 8to scan the whole area of the member 55. The transfer of charge occursagain, which charge this time is positive and hence neutralize thecharge which exists already on the record member. The neutralizationoccurs imagewise so that the remaining charge on the record member willconform in pattern to the original. In other words, the electrostaticlatent image on the record member 50, when developed, provides apositive.

In the process using a record member having a mesh layer, the radiationsensitive member may also be formed with a latent image previously, thatis, before it is placed in contact with the record member. Such mannerof operation is schematically shown in FIGS. 13a to 13. Initially, acorona charger 65 is connected with a DC source 9' of high voltage andis moved over the radiation sensitive layer 58 of a radiation sensitivemember 55 (FIG. 13a). The conductive substrate of the member is earthedas is the negative terminal of the source. The layer 58 is uniformlycharged positive. Then, FIG. 13b, the member 55 is exposed imagewise toradiation 12, whereby the charge in the irradiated areas will disappear.Subsequently, the member 55 is superimposed with a record member 50 ofthe form shown in FIG. 9d and the both members are pressed together byusing an electrode 8 of soft, elastic conductive material and a backingsupport 8'. When switch 10 is closed to apply a positive potential tothe member 55 (FIG. 13c), the latent image thereon is transferred to therecord member. Upon opening switch 10, switch 11 is closed and then themember 55 is removed. Development of the resulting latent image on therecord member provides a positive.

Several examples of a record member shown in FIG. 9 and the processusing such member will be given below.

12 EXAMPLE 6 On a 50 micron thick paper of high quality was coated asubstratum of polyvinyl alcohol to a thickness of 5 microns and on thesubstratum was coated a film of polystyrene resin 10 microns thick. Theresulting composite is equivalent to a commercially availableelectrostatic recording paper. On the resin film was applied aninsulating mesh layer, 8 microns thick, of polyvinyl butyral resin,using the copperplate printing technique mentioned previously. Thecopperplate ink comprised a 20% resin solution in alcohol. On the otherhand, a photosensitive member was prepared by coating a conductive filmof tin oxide, or Nesa film, on one surface of a hard glass plate 2 mm.thick, and by evaporating a 50 micron thick film of amorphous seleniumon the conductive film. The both members were used in the process shownin FIG. 10, using a voltage of +750 volts and an exposure for a quarterof a second to a light output from a photographic enlarging deviceproviding maximum illumination of luxes on the image surface. The imageon the record member was satisfactory.

EXAMPLE 7 On a paper of high quality, 50 microns thick, was coated asubstratum of polyvinyl alcohol, 5 microns thick, and on the substratumwas coated a 12 micron thick film of polystyrene resin. On the surfaceof the resin film was formed a mesh layer using the heated rolltechnique, thereby obtaining a record member of the form shown in FIG.9d. The meshwork was 200 meshes and individual dots were in the form ofa truncated cone having a heigh of 8 microns, top diameter of about 40microns and bottom diameter of about 50 microns. This record member wasused together with the photosensitive member described in Example 6 inthe process shown in FIG. 10 with the alternative that the electrode 8comprised a conductive rubber sheet of 1 cm. in thickness and havinghardness of 30 (HS). Applying a pressure of 500 gr./cm. to the rubbersheet and using a voltage of +750 volts and exposure for one second to aphotographic enlarging device which provides maximum illumination of 20luxes on the image surface, an image of good quality was obtained.

EXAMPLE 8 On a 12.5 micron thick film of polyethylene terephtalate(Mylar) was coated photoresist KPR available from Eastman Kodak Companyto a thickness of 8 microns. A meshwork of 200 meshes was held incontact with the photoresist layer and the latter was exposed toultraviolet ray. A developer comprising principally trichlene wasapplied to the photoresist to dissolve those parts which had not beenpolymerized, thereby obtaining a record member of the form shown in FIG.9a. The record member was used in the same process as in Example 7 andprovided a latent image of good quality.

EXAMPLE 9 A polystyrene film of 30 microns in thickness was tensioned ona rubber-lined drum of 50 cm. in diameter, and a roller matrix made fromcopper and having a diameter of 10 cm. and heated to C. was held againstthe polystyrene film under pressure. Rotating the drum at a peripheralspeed of 3 m./min., dots of 8 microns in height and 200 meshes wereformed in the surface of the polystyrene film. The film was removed fromthe drum and on its back was applied a 1 micron thick layer of copperiodide, thereby forming a record member of the form shown in FIG. 9b. Onthe other hand, a photoconductive member was prepared by evaporatingamorphous selenium to a thickness of 50 microns on an aluminium plate 2mm. thick. The record member and radiation sensitive member thusprepared were used in the process illustrated in FIG. 11 with the innerspace enclosed by the film 60 being evacuated to 0.8 atm. Applying+l,500 volts to the record member and using an exposure for one secondto a photographic enlarging device providing maximum illumination of 20luxes on the image surface, a satisfactory latent image was obtained.

2. An electrophotographic process according to claim 1 wherein said meshlayer has a thickness from 0.5 to 100 microns, a resistivity not lessthan 109 Omega cm. and surface resistance not less than 109 Omega persquare.
 3. An electrophotographic process according to claim 1, in whichsaid member for receiving and transferring an image is previously formedwith an electrostatic latent image hereon, and then transferring thepreformed image onto the record member upon application of the voltageacross the members while being held in contact.
 4. Anelectrophotographic process according to claim 1 further comprising thestep of subjecting said radiation sensitive layer to imagewise exposureduring the step of applying the said voltage to form the said latentimage to be transferred to said insulating record member.
 5. Anelectrophotographic process for inducing an electrostatic latent imageon an insulating record member which has an insulating recording layerand an insulating surface layer which surface layer comprises a meshpattern comprising the steps of placing said record member inface-to-face contact with a radiation sensitive member which has aradiation sensitive layer, said radiation sensitive layer becomingconductive upon exposure to radiation, exposing said radiation sensitivelayer to radiation to form a latent image thereon either before or aftercontacting said members, said insulating mesh layer being maintainedbetween the said contacted members, and applying a voltage across saidmembers to charge the insulating record member in accordance with saidlatent image in areas opposite to the radiated areas of the radiationsensitive layer.
 6. An electrophotographic process according to claim 5,wherein said mesh layer has a thickness from 0.5 to 100 microns, aresistivity not less than 109 Omega cm. and surface resistance not lessthan 109 Omega per square.
 7. An electrophotographic process accordingto claim 5 further comprising the step of subjecting said radiationsensitive layer to imagewise exposure during the step of applying thesaid voltage to form the said latent image to be transferred to saidinsulating record member.
 8. An electrophotographic process for inducingan electrostatic latent image on an insulating record member comprisingthe steps of placing a radiation sensitive member, which member becomesconductive upon exposure to radiation exposing said record sensitivemember to radiation to form a latent image thereon after contacting saidmembers in face-to-face contact with an insulating intermediate recordmember, the intermediate member having an insulating recording layer andan insulating surface layer of a mesh pattern thereon, the insulatingmesh layer abutting against the radiation sensitive member, applying afirst voltage across said members to charge the intermediate recordmember in accordance with said latent image, placing the intermediatemember in face-to-face contact with a final record member such that thesaid mesh layer is sandwiched between the said intermediate and finalrecord members to charge the final record member in accordance with thelatent image on the intermediate record member.
 9. An electrographicprocess for inducing an electrostatic latent image on at least oneinsulating record member comprising the steps of placing said insulatingrecord member in face-to-face contact with a normally insulating memberwhich member becomes conductive upon exposure To radiation, exposingsaid member to radiation to form a latent image thereon either before orafter contacting said members, forming a thin insulating layer having amesh pattern on one of said members, maintaining said mesh between saidcontacted members and applying a voltage across said members to chargethe insulating record member in accordance with latent image.
 10. Theelectrophotographic process specified in claim 9 further comprising thesteps of removing said applied voltage and shorting said members toretain the transferred image on said insulating record member.
 11. Theelectrographic process as specified in claim 9 in which said member forreceiving and transferring an image is previously formed with anelectrophotographic process as specified in claim 9 in which said memberfor receiving and transferring an image is previously formed with anelectrostatic latent image thereon.